3D image sensor

ABSTRACT

A three-dimensional (3D) image sensor includes a first substrate having an upper pixel. The upper pixel includes a photoelectric element and first and second photogates connected to the photoelectric element. A second substrate includes a lower pixel, which corresponds to the upper pixel, that is spaced apart from the first substrate in a vertical direction. The lower pixel includes a first transfer transistor that transmits a first signal provided by the first photogate. A first source follower generates a first output signal in accordance with the first signal. A second transfer transistor transmits a second signal provided by the second photogate. A second source follower generates a second output signal in accordance with the second signal. First and second bonding conductors are disposed between the first and second substrates and electrically connect the upper and lower pixels.

This is a Continuation of U.S. application Ser. No. 16/124,226, filedSep. 7, 2018, and a claim of priority is made to Korean PatentApplication No. 10-2018-0027839, filed on Mar. 9, 2018, and all thebenefits accruing therefrom under 35 U.S.C. § 119, the disclosures ofwhich are incorporated herein by reference in their entireties.

BACKGROUND 1. Field

The present disclosure relates to a three-dimensional (3D) image sensor.

2. Description of the Related Art

As digital cameras, digital camcorders, and mobile phones having acamera or camcorder function have been widely used, developments haverecently been made in the field of image sensors. Image sensors aresemiconductor devices for converting an optical image into an electricsignal. Since the demand for stereoscopic images has increased, researchhas been vigorously conducted on three-dimensional (3D) image sensorscapable of capturing both color images and depth images, i.e., depthsensors.

Since depth sensors generally have larger pixels than typical imagesensors, the size of an entire device including the pixels may increase.In order to address this problem, a method is needed to reduce the sizeof pixels and thus to improve the integration density and efficiency ofan image sensor.

SUMMARY

Example embodiments of the present disclosure provide athree-dimensional (3D) image sensor having the size of pixels thereofreduced and thus having an improved integration density.

However, example embodiments of the present disclosure are notrestricted to those set forth herein. The above and other exampleembodiments of the present disclosure will become more apparent to oneof ordinary skill in the art to which the present disclosure pertains byreferencing the detailed description of the present disclosure givenbelow.

According to an example embodiment of the present disclosure, there isprovided a 3D image sensor including a first substrate including anupper pixel, the upper pixel including a photoelectric element and firstand second photogates connected to the photoelectric element; a secondsubstrate including a lower pixel, which corresponds to the upper pixel,and spaced apart from the first substrate in a vertical direction, thelower pixel including a first transfer transistor transmitting a firstsignal provided by the first photogate, a first source followergenerating a first output signal in accordance with the first signal, asecond transfer transistor transmitting a second signal provided by thesecond photogate, and a second source follower generating a secondoutput signal in accordance with the second signal; and first and secondbonding conductors disposed between the first and second substrates andelectrically connecting the upper and lower pixels.

According to another example embodiment of the present disclosure, thereis provided a 3D image sensor including a pixel array divided between afirst substrate and a second substrate, which is disposed below thefirst substrate, and in which a plurality of pixels is arranged in rowsin a first direction and in columns in a second direction; and a bondingconductor array connecting the first and second substrates and in whicha plurality of bonding conductors is arranged in rows in a thirddirection and in columns in a fourth direction that is orthogonal to thethird direction, wherein two bonding conductors are disposed for each ofthe plurality of the pixels, and the first and third directions areinclined at an angle of 45°.

According to still another example embodiment of the present disclosure,there is provided a 3D image sensor including a first substrateincluding an upper pixel array; a second substrate including a lowerpixel array and disposed below the first substrate; and bondingconductors forming a pixel array by connecting the upper and lower pixelarrays, wherein each of the bonding conductors includes a first paddisposed on a bottom surface of the first substrate, a first conductiveball disposed below the first pad, a second pad formed on a top surfaceof the second substrate, and a second conductive ball placed in contactwith the first conductive ball, and a direction in which the pixel arrayis aligned is inclined with respect to a direction in which the bondingconductors are aligned.

According to still another example embodiment of the present disclosure,there is provided a three-dimensional image sensor having a pixel with afirst sub-pixel disposed on a first substrate and a second sub-pixeldisposed on a second substrate. A bonding conductor directly,electrically connects the first sub-pixel and the second sub-pixel andis disposed directly between the first substrate and the secondsubstrate.

Other features and example embodiments may be apparent from thefollowing detailed description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other example embodiments and features of the presentdisclosure will become more apparent by describing in detail exampleembodiments thereof with reference to the attached drawings, in which:

FIG. 1 is a perspective view of a three-dimensional (3D) image sensoraccording to some example embodiments of the present disclosure;

FIG. 2 is a plan view of a first substrate of the 3D image sensor ofFIG. 1 ;

FIG. 3 is a plan view of a second substrate of the 3D image sensor ofFIG. 1 ;

FIG. 4 is a cross-sectional view taken along line A-A′ of FIG. 1 ;

FIG. 5 is an enlarged cross-sectional view of part B of FIG. 4 ;

FIG. 6 is a block diagram of an image sensing apparatus including the 3Dimage sensor according to some example embodiments of the presentdisclosure;

FIG. 7 is a layout view of a pixel array of FIG. 6 ;

FIG. 8 is an equivalent circuit diagram of an example pixel of the pixelarray of FIG. 6 ;

FIG. 9 is an equivalent circuit diagram of another example pixel of thepixel array of FIG. 6 ;

FIG. 10 is a graph for explaining phase sampling of the 3D image sensoraccording to some example embodiments of the present disclosure;

FIG. 11 is a layout view showing the arrangement of pixels and bondingconductors of the 3D image sensor according to some example embodimentsof the present disclosure;

FIG. 12 is a layout view showing the arrangement of pixels and bondingconductors of a 3D image sensor according to some example embodiments ofthe present disclosure;

FIG. 13 is a layout view showing the arrangement of pixels and bondingconductors of a 3D image sensor according to some example embodiments ofthe present disclosure;

FIG. 14 is a bottom view of a first substrate for explaining a pixelregion and a peripheral region of a 3D image sensor according to someexample embodiments of the present disclosure;

FIG. 15 is a partial layout view showing the arrangement of bondingconductors in parts C and D of FIG. 14 ; and

FIG. 16 is a partial layout view showing the arrangement of bondingconductors of a 3D image sensor according to some example embodiments ofthe present disclosure.

DETAILED DESCRIPTION

An image sensor according to some example embodiments of the presentdisclosure will hereinafter be described with reference to FIGS. 1through 11 .

FIG. 1 is a perspective view of a three-dimensional (3D) image sensoraccording to some example embodiments of the present disclosure.

Referring to FIG. 1 , the 3D image sensor according to some exampleembodiments of the present disclosure includes a first substrate 100, asecond substrate 200, and bonding conductors 300.

The first substrate 100 may be disposed on a horizontal plane. Thehorizontal plane may be defined by first and second directions X and Y.Specifically, the first and second directions X and Y may be orthogonalto each other. The first and second directions X and Y may be directionsdefining the width and the length of the first substrate 100. The firstsubstrate 100 may be disposed on a plane defined by the first and seconddirections X and Y.

A third direction Z may be a direction orthogonal to both the first andsecond directions X and Y. Thus, the first, second, and third directionsX, Y, and Z may be orthogonal to one another. If the plane defined bythe first and second directions X and Y is the horizontal plane, thethird direction Z may be defined as a vertical direction.

The first substrate 100 may include a first top surface 101 and a firstbottom surface 102. The first top surface 101 and the first bottomsurface 102 of the first substrate 100 may be surfaces of the firstsubstrate 100 that are opposite to each other in the third direction Z.

The second substrate 200 may be spaced apart from the first substrate100 in the third direction Z. That is, the second substrate 200 may bedisposed below the first substrate 100. The second substrate 200 maycorrespond to the first substrate 100. Specifically, the secondsubstrate 200 may completely overlap with the first substrate 100 in thethird direction Z. The first and second substrates 100 and 200 may sharethe same horizontal cross-section and may completely overlap with eachother, but the present disclosure is not limited thereto.

The second substrate 200 may include a second top surface 201 and asecond bottom surface 202. The second top surface 201 and the secondbottom surface 202 of the second substrate 200 may be surfaces of thesecond substrate 200 that are opposite to each other in the thirddirection Z.

The bonding conductors 300 may be disposed between the first and secondsubstrates 100 and 200. The bonding conductors 300 may be placed incontact with the first bottom surface 102 of the first substrate and thesecond top surface 201 of the second substrate 200. That is, the bondingconductors 300 may be disposed between the first and second substrates100 and 200 along the third direction Z.

The bonding conductors 300 may electrically connect the first and secondsubstrates 100 and 200. The bonding conductors 300 may comprise aconductor. The bonding conductors 300 may comprise, for example, copper(Cu), but the present disclosure is not limited thereto.

A plurality of bonding conductors 300 may be provided. The plurality ofbonding conductors 300 may be aligned to form a bonding conductor array,and this will be described later in detail.

FIG. 2 is a plan view of the first substrate of the 3D image sensor ofFIG. 1 .

Referring to FIG. 2 , the first substrate 100 may have a first pixelregion R_(Px1) and a first peripheral region R_(Pr1).

The first pixel region R_(Px1) may be a region in which the pixels ofthe 3D image sensor according to some example embodiments of the presentdisclosure are disposed. The first pixel region R_(Px1) may besurrounded by the first peripheral region R_(Pr1) in a plan view. Thefirst pixel region R_(Px1) may be a region receiving light from theoutside.

The first peripheral region R_(Pr1) may surround the first pixel regionR_(Px1). That is, the first peripheral region R_(Pr1) may be theperipheral region of the first pixel region R_(Px1). In the firstperipheral region R_(Pr1), circuits that process signals generated inthe first pixel region R_(Px1) may be disposed.

FIG. 3 is a plan view of the second substrate of the 3D image sensor ofFIG. 1 .

Referring to FIG. 3 , the second substrate 200 may have a second pixelregion R_(Px2) and a second peripheral region R_(Pr2).

The second pixel region R_(Px2) may be a region in which the pixels ofthe 3D image sensor according to some example embodiments of the presentdisclosure are disposed. The second pixel region R_(Px2) may besurrounded by the second peripheral region R_(Pr2) in a plan view. Thesecond pixel region R_(Px2) may be a region receiving light from theoutside.

The second peripheral region R_(Pr2) may surround the second pixelregion R_(Px2). That is, the second peripheral region R_(Pr2) may be theperipheral region of the second pixel region R_(Px2). In the secondperipheral region R_(Pr2), circuits that process signals generated inthe second pixel region R_(Px2) may be disposed.

Referring to FIGS. 1 through 3 , the first and second pixel regionsR_(Px1) and R_(Px2) may overlap with each other in the third directionZ. Also, the first and second peripheral regions R_(Pr1) and R_(Pr2) mayoverlap with each other in the third direction Z. That is, the pixelregions of the first and second substrates 100 and 200 may be disposedto overlap with each other, and the peripheral regions of the first andsecond substrates 100 and 200 may be disposed to overlap with eachother.

The bonding conductors 300 may connect the first and second pixelregions R_(Px1) and R_(Px2), and may connect the first and secondperipheral regions R_(Pr1) and R_(Pr2). The first and second pixelregions R_(Px1) and R_(Px2) may be connected together by the bondingconductors 300 and may thus form a complete pixel region. That is, thecomplete pixel region may be divided into the first and second pixelregions R_(Px1) and R_(Px2) of the first and second substrates 100 and200, and the first and second pixel regions R_(Px1) and R_(Px2) may beconnected together by the bonding conductors 300.

FIG. 4 is a cross-sectional view taken along line A-A′ of FIG. 1 .

Referring to FIGS. 1 through 4 , the bonding conductors 300 includeperipheral bonding conductors 301 and pixel bonding conductors 302.

The peripheral bonding conductors 301 may be formed in a peripheralregion R_(Pr). The peripheral region R_(Pr) may be a region defined bythe first and second peripheral regions R_(Pr1) and R_(Pr2) overlappingwith each other in the third direction Z. The pixel bonding conductors302 may be formed in a pixel region R_(Px). The pixel region R_(Px) maybe a region defined by the first and second pixel regions R_(Px1) andR_(Px2) overlapping with each other in the third direction Z.

That is, the pixel region R_(Px) may be surrounded by the peripheralregion R_(Pr). The pixel region R_(Px) and the peripheral region R_(Pr)may be defined commonly on both the first and second substrates 100 and200.

The peripheral bonding conductors 301 of the peripheral region R_(Pr)may have a first thickness T1. A plurality of peripheral bondingconductors 301 may be provided in the peripheral region R_(Pr). Theplurality of peripheral bonding conductors 301 may be uniformly spacedapart from one another by a first distance d1.

The pixel bonding conductors 302 of the pixel region R_(Px) may have asecond thickness T2. A plurality of pixel bonding conductors 302 may beprovided in the pixel region R_(Px). The plurality of pixel bondingconductors 302 may be uniformly spaced apart from one another by asecond distance d2.

Since the peripheral region R_(Pr) may have more room for thearrangement of the bonding conductors 300 than the pixel region R_(Px),the first thickness T1 may be greater than the second thickness T2, butthe present disclosure is not limited thereto. Thus, by making thethickness of the peripheral bonding conductors 301 greater than thethickness of the pixel bonding conductors 302, the connection resistancebetween the first and second substrates 100 and 200 can be reduced inthe peripheral region R_(Pr). As a result, the reliability of signalstransmitted between the first and second substrates 100 and 200 can befurther improved in the peripheral region R_(Pr).

Since the peripheral region R_(Pr) may have more room for thearrangement of the bonding conductors 300 than the pixel region R_(Px),the first distance d1 may be greater than the second distance d2, butthe present disclosure is not limited thereto. Thus, by making thedistance between the peripheral bonding conductors 301 greater than thedistance between the pixel bonding conductors 302, the formation of thebonding conductors 300 can be simplified, and the risk of misalignmentcan be reduced. As a result, the reliability of signals transmittedbetween the first and second substrates 100 and 200 can be furtherimproved in the peripheral region R_(Pr).

FIG. 5 is an enlarged cross-sectional view of part B of FIG. 4 .

Referring to FIG. 5 , a bonding conductor 300 may include a first pad310, a first conductive ball 320, a second pad 340, and a secondconductive ball 330.

The first pad 310 may be disposed on the first bottom surface 102 of thefirst substrate 100. The first pad 310 may be connected to wires and viastructures formed in the first substrate 100 and may thus beelectrically connected to circuits disposed on the first substrate 100.

The second pad 340 may be disposed on the second top surface 201 of thesecond substrate 200. The second pad 340 may be connected to wires andvia structures formed in the second substrate 200 and may thus beelectrically connected to circuits disposed on the second substrate 200.

The first conductive ball 320 may be disposed on an exposed surface ofthe first pad 310, i.e., below the first substrate 100. The firstconductive ball 320 may be placed in direct contact with, andelectrically connected to, the first pad 310.

The second conductive ball 330 may be disposed on an exposed surface ofthe second pad 340, i.e., above the second substrate 200. The secondconductive ball 330 may be placed in direct contact with, andelectrically connected to, the second pad 340.

The first and second conductive balls 320 and 330 may be placed incontact with each other in a vertical direction, i.e., the thirddirection Z. Since the first and second conductive balls 320 and 330 areplaced in contact with each other, the first and second substrates 100and 200 may be electrically connected. Specifically, electric signalsmay be transmitted between the first and second substrates 100 and 200via the first pad 310, the first conductive ball 320, the secondconductive ball 330, and the second pad 340.

The size and the arrangement of, and the distance between, theperipheral bonding conductors 301 and the size and the arrangement of,and the distance between, the pixel bonding conductors 302 may vary, butthe structure of the bonding conductor 300 of FIG. 5 may directly applyto both the peripheral bonding conductors 301 and the pixel bondingconductors 302.

FIG. 6 is a block diagram of an image sensing apparatus including the 3Dimage sensor according to some example embodiments of the presentdisclosure.

Referring to FIG. 6 , the image sensing apparatus includes an infrared(IR) emitter 400 and a 3D image sensor 90.

The IR emitter 400 may apply a pulse signal L1 to an object O. The pulsesignal L1 may be IR light. The pulse signal L1 may be reflected by theobject O, and as a result, a reflected pulse signal L2 may return to the3D image sensor 90 via a lens 91. The IR emitter 400 may transmitinformation regarding the pulse signal L1 to the 3D image sensor 90.

The 3D image sensor 90 may analyze color information and distanceinformation of the object O, i.e., 3D image information of the object O,using the reflected pulse signal L2.

Specifically, the 3D image sensor 90 includes a pixel array 10, in whichpixels each having a photoelectric element are arrangedtwo-dimensionally, a timing generator 20, a row decoder 30, a row driver40, a correlated double sampler (CDS) 50, an analog-to-digital converter(ADC) 60, a readout circuit (e.g., latch) 70, and a column decoder 80.

The pixel array 10 may include a plurality of pixels which is arrangedtwo-dimensionally. The plurality of pixels converts an optical imageinto an electric output signal. The pixel array 10 may receive thereflected pulse signal L2 via the lens 91.

The pixel array 10 may be driven by receiving a plurality of drivingsignals such as a row selection signal, a reset signal, and a chargetransfer signal from the row driver 40. The electric output signalobtained by the pixel array 10 is provided to the CDS 50 via a verticalsignal line.

The timing generator 20 provides a timing signal and a control signal tothe row decoder 30 and the column decoder 80. The timing generator 20may receive information regarding the pulse signal L1 from the IRemitter 400.

The row decoder 30 may generate driving signals for driving each row ofpixels of the pixel array 10 such as, for example, a transfer signal, areset signal, and a select signal, and a gate signal.

The row driver 40 may provide a plurality of driving signals for theplurality of pixels to the pixel array 10 in accordance with the resultof decoding performed by the row decoder 30. In a case where theplurality of pixels is arranged in a matrix having a plurality of rows,the row driver 40 may provide the plurality of driving signals in unitsof the plurality of rows.

The CDS 50 may receive the output signal of the pixel array 10 via thevertical signal line and may hold and sample the received signal. Thatis, the CDS 50 may double-sample a particular noise level and the levelof the output signal of the pixel array 10 and may output the differencebetween the particular noise level and the output signal of the pixelarray 10.

The ADC 60 may convert an analog signal corresponding to the differencebetween the particular noise level and the output signal of the pixelarray 10 into a digital signal and may output the digital signal.

A read-out circuit 70 may perform image processing on the digital signaloutput by the ADC 60 in accordance with the result of decoding performedby the row decoder 30. As a result, the read-out circuit 70 may obtainthe color information and the depth information of the object O.

The CDS 50, the ADC 60, the read-out circuit 70, the row driver 40, therow decoder 30, and the column decoder 80 may be disposed in theperipheral region R_(Pr) of FIG. 4 , but the present disclosure is notlimited thereto.

FIG. 7 is a layout view of the pixel array of FIG. 6 .

Referring to FIGS. 1 through 3 and 7 , in the pixel array 10, aplurality of pixels may be aligned in rows and columns. Referring toFIG. 7 , a pixel P(i,j) refers to a pixel in an i-th row and a j-thcolumn. FIG. 7 illustrates an example in which there are three rows andthree columns of pixels in the pixel array 10, but the presentdisclosure is not limited thereto. That is, the numbers of rows andcolumns of pixels in the pixel array 10 may vary.

The pixel P(i,j) may be disposed in the pixel region R_(Px). The pixelP(i,j) may be divided between the first and second pixel regions R_(Px1)and R_(Px2). Part of the pixel P(i,j) disposed in the first pixel regionR_(Px1), i.e., an upper pixel, and part of the pixel P(i,j) disposed inthe second pixel region R_(Px2), i.e., a lower pixel, may overlap witheach other in the vertical direction, i.e., the third direction Z. Thus,the planar arrangement of the pixel array 10 may be defined within agiven horizontal area, as shown in FIG. 7 , regardless of the divisionof the pixel P(i,j) into upper and lower pixels.

The pixel P(i,j) may be rectangular in shape, but the present disclosureis not limited thereto. The pixel P(i,j) may be disposed to adjoin otherpixels on the sides thereof.

The P(i,j) may receive an input Vin and may produce an output Vout. Theinput Vin may be provided to the pixel array 10 in units of the rows ofthe pixel array 10, and the output Vout may be produced in units of thecolumns of the pixel array 10.

FIG. 8 is an equivalent circuit diagram of an example pixel of the pixelarray of FIG. 6 .

Referring to FIG. 8 , the pixel P(i,j) may include an upper pixel P1, alower pixel P2, and pixel bonding conductors 302.

The upper pixel P1 may be formed in the first pixel region R_(Px1) ofthe first substrate 100. The lower pixel P2 may be formed in the secondpixel region R_(Px2) of the second substrate 200. The upper and lowerpixels P1 and P2, which are the elements of the pixel P(i,j), aredivided between two substrates, and as a result, the horizontal area ofthe pixel P(i,j) can be minimized.

The pixel bonding conductors 302 may electrically connect the upper andlower pixels P1 and P2. The pixel bonding conductors 302 may includefirst and second pixel bonding conductors 302 a and 302 b. That is, twopixel bonding conductors 302 may be provided for the pixel P(i,j)because the pixel P(i,j) is a 2-tap pixel having two photogates.

If the pixel P(i,j) is a 3- or 4-tap pixel having three or fourphotogates, three or four pixel bonding conductors 302 may be providedfor the pixel P(i,j). That is, the number of photogates provided in thepixel P(i,j) may be the same as the number of pixel bonding conductors302 provided in the pixel P(i,j).

The upper pixel P1 may include a photoelectric element PD, a firstphotogate PGA, and a second photogate PGB. The lower pixel P2 mayinclude a first transfer transistor TG1, a second transfer transistorTG2, a first reset transistor RG1, a second reset transistor RG2, afirst source follower S/F1, a second source follower S/F2, a firstselect transistor SEL1, and a second select transistor SEL2.

The photoelectric element PD may be an element that converts lightapplied thereto into electric charges. The photoelectric element PD mayconvert light into an electric signal working with the first and secondphotogates PGA and PGB.

Specifically, the photoelectric element PD may sense light. Thephotoelectric element PD may generate electron-hole pairs (EHPs) basedon the sensed light. A depletion region is formed by a gate voltageapplied to the first photogate PGA, and due to the depletion region, theelectrons and holes of the EHPs are separated. The separated electronsare accumulated below the first photogate PGA.

The first photogate PGA is connected to the drain of the first transfertransistor TG1, and a first floating diffusion region FD1 is connectedto the source of the first transfer transistor TG1. The first transfertransistor TG1 transmits the electrons below the first photogate PGA inresponse to the gate voltage applied to the first photogate PGA. Thefirst transfer transistor TG1 electrically connects or disconnects thefirst photogate PGA and the first floating diffusion region FD1 inresponse to a gate signal.

The first floating diffusion region FD1 is connected to the gate of thefirst source follower S/F1, a power supply voltage VDD is connected tothe drain of the first source follower S/F1, and the first selecttransistor SEL1 is connected to the source of the first source followerS/F1. The voltage of the source of the first source follower S/F1 isdetermined by the voltage of the first floating diffusion region FD1.The voltage of the first floating diffusion region FD1 is determined bythe amount of electrons transmitted from the first photogate PGA.

A row control signal is connected to the gate of the first selecttransistor SEL1, the source of the first source follower S/F1 isconnected to the drain of the first select transistor SEL1, and anoutput line of the pixel array 10 is connected to the source of thefirst select transistor SEL1.

The power supply voltage VDD is connected to the drain of the firstreset transistor RG1, and the first floating diffusion region FD1 isconnected to the source of the first reset transistor RG1 through thefirst transfer transistor TG1. When the detection of pixel informationis performed based on the voltage of the first floating diffusion regionFD1 and then the gate of the first reset transistor RG1 is activated bya first reset signal, the first reset transistor RG1 resets the voltageof the first floating diffusion region FD1 to the power supply voltageVDD.

When the photoelectric element PD senses light, a depletion region isformed by a gate voltage applied to the second photogate PGB, and due tothe depletion region, the electrons and holes of EHPs are separated. Theseparated electrons are accumulated below the second photogate PGB.

The second photogate PGB is connected to the drain of the secondtransfer transistor TG2, and a second floating diffusion region FD2 isconnected to the source of the second transfer transistor TG2. Thesecond transfer transistor TG2 transmits the electrons below the secondphotogate PGB in response to the gate voltage applied to the secondphotogate PGB. The second transfer transistor TG2 electrically connectsor disconnects the second photogate PGB and the second floatingdiffusion region FD2 in response to a gate signal.

The second floating diffusion region FD2 is connected to the gate of thesecond source follower S/F2, the power supply voltage VDD is connectedto the drain of the second source follower S/F2, and the second selecttransistor SEL2 is connected to the source of the second source followerS/F2. The voltage of the source of the second source follower S/F2 isdetermined by the voltage of the second floating diffusion region FD2.The voltage of the second floating diffusion region FD2 is determined bythe amount of electrons transmitted from the second photogate PGB.

A row control signal is connected to the gate of the second selecttransistor SEL2, the source of the second source follower S/F2 isconnected to the drain of the second select transistor SEL2, and anoutput line of the pixel array 10 is connected to the source of thesecond select transistor SEL2.

The power supply voltage VDD is connected to the drain of the secondreset transistor RG2, and the second floating diffusion region FD2 isconnected to the source of the second reset transistor RG2 through thesecond transfer transistor TG2. When the detection of pixel informationis performed based on the voltage of the second floating diffusionregion FD2 and then the gate of the second reset transistor RG2 isactivated by a second reset signal, the second reset transistor RG2resets the voltage of the second floating diffusion region FD2 to thepower supply voltage VDD.

The upper and lower pixels P1 and P2 may be electrically connectedbetween the first photogate PGA and the first transfer transistor TG1and between the second photogate PGB and the second transfer transistorTG2 by the pixel bonding conductors 302. Specifically, the upper andlower pixels P1 and P2 may be connected between the first photogate PGAand the first transfer transistor TG1 by the first pixel bondingconductor 302 a and may be connected between the second photogate PGBand the second transfer transistor TG2 by the second pixel bondingconductor 302 b.

The pixel P(i,j) of the 3D image sensor according to some exampleembodiments of the present disclosure may be configured to have astructure other than that illustrated in FIG. 8 .

FIG. 9 is an equivalent circuit diagram of another example pixel of thepixel array of FIG. 6 .

Referring to FIG. 9 , the first reset transistor RG1 may be connectedbetween the first source follower S/F1 and the first transfer transistorTG1, rather than between the first photogate PGA and the first transfertransistor TG1.

Similarly, the second reset transistor RG2 may be connected between thesecond source follower S/F2 and the second transfer transistor TG2,rather than between the second photogate PGB and the second transfertransistor TG2.

The pixel P(i,j) may include various circuit configurations to producethe same result.

Referring to FIGS. 7 through 9 , the input Vin may include the powersupply voltage VDD and the gate voltage of each transistor. That is, theinput Vin may include the gate voltages of the first photogate PGA, thefirst transfer transistor TG1, the first reset transistor RG1, the firstselect transistor SEL1, the second photogate PGB, the second transfertransistor TG2, the second reset transistor RG2, and the second selecttransistor SEL2.

The output Vout may include a first output VOUTA and a second outputVOUTB.

FIG. 10 is a graph for explaining phase sampling of the 3D image sensoraccording to some example embodiments of the present disclosure.Referring to FIG. 10 , the horizontal axis represents time (t), and thevertical axis represents brightness (B). FIG. 10 shows an example pulsesignal L1 and an example reflected pulse signal L2.

Referring to FIGS. 6 and 10 , the reflected pulse signal L2 may besampled at four points, i.e., at points t1, t2, t3, and t4 where thephase of the pulse signal L1 is 0 degrees, 90 degrees, 180 degrees, and270 degrees, respectively. Values A₀, A₁, A₂, and A₃ may be measured atthe points t1, t2, t3, and t4, respectively.

Precision information can be obtained from a first measurement value M1.Brightness information can be obtained from a second measurement valueM2. Distance information can be obtained from a third measurement valueM3.

The 3D image sensor according to some example embodiments of the presentdisclosure can acquire both color information and distance informationof the object O using the A₀, A₁, A₂, and A₃ and the first, second, andthird measurement values M1, M2, and M3.

FIG. 11 is a layout view showing the arrangement of the pixels and thebonding conductors of the 3D image sensor according to some exampleembodiments of the present disclosure. FIG. 11 is a layout view in whichthe outlines of pixels and the outlines of bonding conductors overlap.

Referring to FIGS. 8 and 11 , two pixel bonding conductors 302 may beneeded for one pixel. In FIG. 11 , the pixel P(i,j) is defined by afirst outline PX_OL, and the pixel bonding conductors 302 are defined bysecond outlines BC_OL.

If a first outline PX_OL, which is the outline of the pixel P(i,j), is asquare having a length of 2A, two second outlines BC_OL may be providedin the pixel P(i,j) as squares having a length of A.

Each of the second outlines BC_OL simply represents the maximum areathat each of the pixel bonding conductors 302 can occupy, and each ofthe pixel bonding conductors 302 cannot extend beyond, but may notnecessarily occupy entirely, the area defined by each of the secondoutlines BC_OL.

In the 3D image sensors according to some example embodiments of thepresent disclosure, the elements of each pixel are divided between twosubstrates, and as a result, the size of each pixel can be reduced. Thatis, by expanding each pixel in the vertical direction while reducing thehorizontal area of each pixel, the resolution and the integrationdensity of the 3D image sensors according to some example embodiments ofthe present disclosure can both be improved.

A 3D image sensor according to some example embodiments of the presentdisclosure will hereinafter be described with reference to FIG. 12 .Descriptions of elements of the 3D image sensor according to the exampleembodiment of FIG. 12 that are the same as their respective counterpartsof the 3D image sensor according to the example embodiment of FIG. 1will be omitted or at least simplified.

FIG. 12 is a layout view showing the arrangement of pixels and bondingconductors of a 3D image sensor according to some example embodiments ofthe present disclosure.

Referring to FIGS. 1 through 3, 8, and 12 , first outlines PX_OL andsecond outlines BC_OL may be inclined at an angle of 45° with respect toeach other.

That is, the first outlines PX_OL may be aligned in rows in a firstdirection X and in columns in a second direction Y. On the other hand,the second outlines BC_OL may be aligned in rows in a fourth directionK, which is inclined at an angle of 45° with respect to the firstdirection X. The fourth direction K may also be inclined at an angle of45° with respect to the second direction Y. The second outlines BC_OLmay be aligned in columns in a direction that is inclined at an angle of45° with respect to the second direction Y and is orthogonal to thefourth direction K.

Pixels in the same row in the first direction X may receive the sameinput Vin, and pixels in the same column in the second direction Y mayshare the same output Vout.

The second outlines BC_OL may define regions in which pixel bondingconductors 302 are formed, and if not misaligned, the pixel bondingconductors 302 may be disposed at the centers of the regions defined bythe second outlines BC_OL. Thus, since the second outlines BC_OL arealigned in the fourth direction K, the pixel bonding conductors 302 mayalso be aligned in the fourth direction K. That is, the pixel bondingconductors 302 may form a pixel bonding conductor array having thefourth direction K as its row direction and having the directionorthogonal to the fourth direction K as its column direction.

In a case where the pixel bonding conductors 302 are used, there may bea limit in reducing the size of each pixel because two pixel bondingconductors 302 are needed for each pixel.

However, by arranging the pixel bonding conductors 302 at an inclinationof 45° with respect to the pixels, as illustrated in FIG. 12 , thelength of the sides of each pixel can be reduced from 2A to √2A. As aresult, the integration density and the resolution of the 3D imagesensor according to the example embodiment of FIG. 12 can both beimproved.

A 3D image sensor according to some example embodiments of the presentdisclosure will hereinafter be described with reference to FIG. 13 .Descriptions of elements of the 3D image sensor according to the exampleembodiment of FIG. 13 that are the same as their respective counterpartsof any one of the 3D image sensors according to the example embodimentsof FIGS. 1 and 12 will be omitted or at least simplified.

FIG. 13 is a layout view showing the arrangement of pixels and bondingconductors of a 3D image sensor according to some example embodiments ofthe present disclosure.

Referring to FIGS. 1 through 3, 8, and 13 , first outlines PX_OL andsecond outlines BC_OL may be inclined at an angle of 45° with respect toeach other.

The first outlines PX_OL may be aligned in a fourth direction K and adirection orthogonal to the fourth direction K, rather than in first andsecond directions X and Y. On the other hand, the second outlines BC_OLmay be aligned in rows in the first direction X and in columns in thesecond direction Y.

Pixels in the same row in the first direction X may receive the sameinput Vin, and pixels in the same column in the second direction Y mayshare the same output Vout.

Due to this arrangement, the horizontal shape of each pixel may beformed as a square in the direction orthogonal to the fourth directionK. Accordingly, the diagonals of a square defined by the horizontalshape of each square may extend in the first and second directions X andY.

The second outlines BC_OL may define regions in which pixel bondingconductors 302 are formed, and if not misaligned, the pixel bondingconductors 302 may be disposed at the centers of the regions defined bythe second outlines BC_OL. Thus, since the second outlines BC_OL arealigned in the first and second directions X and Y, the pixel bondingconductors 302 may also be aligned in the first and second directions Xand Y. That is, the pixel bonding conductors 302 may form a pixelbonding conductor array having the first direction X as its rowdirection and having the second direction Y as its column direction.

In a case where the pixel bonding conductors 302 are used, there may bea limit in reducing the size of each pixel because two pixel bondingconductors 302 are needed for each pixel.

However, by arranging the pixel bonding conductors 302 at an inclinationof 45° with respect to the pixels, as illustrated in FIG. 13 , thelength of the sides of each pixel can be reduced from 2A to √2A. As aresult, the integration density and the resolution of the 3D imagesensor according to the example embodiment of FIG. 12 can both beimproved.

In addition, the distance between wires for applying an input signal toeach row of pixels for the input Vin may become smaller than in the 3Dimage sensor according to the example embodiment of FIG. 12 .Accordingly, a 3D image sensor having a higher resolution than the 3Dimage sensor according to the example embodiment of FIG. 12 can beprovided.

A 3D image sensor according to some example embodiments of the presentdisclosure will hereinafter be described with reference to FIGS. 14 and15 . Descriptions of elements of the 3D image sensor according to theexample embodiment of FIGS. 14 and 15 that are the same as theirrespective counterparts of any one of the 3D image sensors according tothe example embodiments of FIGS. 1, 12, and 13 will be omitted or atleast simplified.

FIG. 14 is a bottom view of a first substrate for explaining a pixelregion and a peripheral region of a 3D image sensor according to someexample embodiments of the present disclosure, and FIG. 15 is a partiallayout view showing the arrangement of bonding conductors in parts C andD of FIG. 14 .

Referring to FIGS. 14 and 15 , a first substrate 100 may have a firstpixel region R_(Px1) and a first peripheral region R_(Pr1). A secondpixel region R_(Px2) and a second peripheral region R_(Pr2) of a secondsubstrate 200 have the same layout as the first pixel region R_(Px1) andthe first peripheral region R_(Pr1), respectively, of the firstsubstrate 100, and thus, descriptions thereof will be omitted.

In the first pixel region R_(Px1), pixel bonding conductors 302 may bealigned in rows in a fourth direction K and in columns in a directionorthogonal to the fourth direction K. On the other hand, in the firstperipheral region R_(Pr1), peripheral bonding conductors 301 may bealigned in rows in a first direction X and in columns in a seconddirection Y.

Accordingly, the arrangement of the pixel bonding conductors 302 and thearrangement of the peripheral bonding conductors 301 may be inclined atan angle of 45° with respect to each other.

The pixel bonding conductors 302 may be arranged at an inclination inorder to reduce the horizontal area of the first pixel region R_(Px1),but the peripheral bonding conductors 301 do not need to be arranged atan inclination and are thus arranged in a non-diagonal direction becausethe first peripheral region R_(Pr1) may have more room than the firstpixel region R_(Px1).

A 3D image sensor according to some example embodiments of the presentdisclosure will hereinafter be described with reference to FIGS. 14 and16 . Descriptions of elements of the 3D image sensor according to theexample embodiment of FIG. 16 that are the same as their respectivecounterparts of any one of the 3D image sensors according to the exampleembodiments of FIGS. 1, 12, 13, 14, and 15 will be omitted or at leastsimplified.

FIG. 16 is a layout view showing the arrangement of bonding conductorsof a 3D image sensor according to some example embodiments of thepresent disclosure. Specifically, FIG. 16 is a partial enlarged layoutview showing parts of the 3D image sensor according to some exampleembodiments of the present disclosure corresponding to parts C and D ofFIG. 14 .

Referring to FIGS. 14 and 16 , a first substrate 100 may have a firstpixel region R_(Px1) and a first peripheral region R_(Pr1). A secondpixel region R_(Px2) and a second peripheral region R_(Pr2) of a secondsubstrate 200 have the same layout as the first pixel region R_(Px1) andthe first peripheral region R_(Pr1), respectively, of the firstsubstrate 100, and thus, descriptions thereof will be omitted.

Pixel bonding conductors 302 in the first pixel region R_(Px1) may havea second thickness T2, and peripheral bonding conductors 301 in thefirst peripheral region R_(Pr1) may have a first thickness T1. The firstthickness T1 may be greater than the second thickness T2.

The difference between the first and second thicknesses T1 and T2 mayapply not only to a first direction X, but also to a second direction Y.That is, the peripheral bonding conductors 301 may have a largerhorizontal area than the pixel bonding conductors 302.

Specifically, referring to FIG. 5 , the peripheral bonding conductors301 may have larger first pads 310 and larger second pads 340 than thepixel bonding conductors 302. That is, even if the horizontalcross-sectional area of first conductive balls 320 and second conductiveballs 330 of the peripheral bonding conductors 301 is the same as thehorizontal cross-sectional area of first conductive balls 320 and secondconductive balls 330 of the peripheral bonding conductors 301, the firstpads 310 and the second pads 340 of the peripheral bonding conductors301 may be larger than the first pads 310 and the second pads 340 of thepixel bonding conductors 302, but the present disclosure is not limitedthereto.

The horizontal cross-sectional area of the first conductive balls 320and the second conductive balls 330 of the peripheral bonding conductors301 may also be larger than the horizontal cross-sectional area of thefirst conductive balls 320 and the second conductive balls 330 of thepixel bonding conductors 302.

This is because the first peripheral region R_(Pr1) may have more roomthan the first pixel region R_(Px1). Thus, the resistance of theperipheral bonding conductors 301 may become lower.

The pixel bonding conductors 302 in the first pixel region R_(Px1) maybe a second distance d2 apart from one another, and the peripheralbonding conductors 301 in the first peripheral region R_(Pr1) may be afirst distance d1 apart from one another. The first distance d1 may begreater than the second distance d2.

As already described above, this is also because the first peripheralregion R_(Pr1) may have more room than the first pixel region R_(Px1).Accordingly, the fabrication of the peripheral bonding conductors 301can be facilitated. Also, the risk of misalignment can be reduced, andas a result, the reliability of the transmission of signals can beimproved.

As is traditional in the field, embodiments may be described andillustrated in terms of blocks which carry out a described function orfunctions. These blocks, which may be referred to herein as units ormodules or the like, are physically implemented by analog and/or digitalcircuits such as logic gates, integrated circuits, microprocessors,microcontrollers, memory circuits, passive electronic components, activeelectronic components, optical components, hardwired circuits and thelike, and may optionally be driven by firmware and/or software. Thecircuits may, for example, be embodied in one or more semiconductorchips, or on substrate supports such as printed circuit boards and thelike. The circuits constituting a block may be implemented by dedicatedhardware, or by a processor (e.g., one or more programmedmicroprocessors and associated circuitry), or by a combination ofdedicated hardware to perform some functions of the block and aprocessor to perform other functions of the block. Each block of theembodiments may be physically separated into two or more interacting anddiscrete blocks without departing from the scope of the disclosure.Likewise, the blocks of the embodiments may be physically combined intomore complex blocks without departing from the scope of the disclosure.

In concluding the detailed description, those skilled in the art willappreciate that many variations and modifications can be made to thepreferred embodiments without substantially departing from theprinciples of the present disclosure. Therefore, the disclosed preferredembodiments of the disclosure are used in a generic and descriptivesense only and not for purposes of limitation.

What is claimed is:
 1. A three-dimensional (3D) image sensor comprising:a first substrate including an upper pixel array, a plurality of upperpixels of the upper pixel array are disposed in first rows and firstcolumns of a first arrangement; a second substrate including a lowerpixel array including a plurality of lower pixels; and a bondingconductor array disposed between the first and second substrates, aplurality of bonding conductors of the bonding conductor array aredisposed in second rows and second columns of a second arrangement andelectrically connected between the upper pixel array and the lower pixelarray, wherein the second arrangement is inclined at an angle of 45°with respect to the first arrangement.
 2. The 3D image sensor of claim1, wherein the number of the bonding conductors in a pixel unit is sameas the number of photogates in the upper pixel of the pixel unit.
 3. The3D image sensor of claim 1, wherein horizontal cross sections of theupper and lower pixels are in a shape of a rectangle and overlap witheach other in the vertical direction.
 4. The 3D image sensor of claim 3,wherein the bonding conductors are aligned along diagonals of therectangle.
 5. The 3D image sensor of claim 4, wherein the firstarrangement includes rows in a first direction and columns in a seconddirection in planar, the second arrangement includes rows in a thirddirection and columns in a fourth direction in the planar, and the firstdirection is inclined to the third direction and the second direction isinclined to the fourth direction.
 6. The 3D image sensor of claim 1,wherein the bonding conductor includes peripheral bonding conductorsdisposed in a peripheral region and pixel bonding conductors in a pixelregion, the pixel region is surrounded by the peripheral region, whereina thickness of the peripheral bonding conductor is greater than athickness of the pixel bonding conductor.
 7. The 3D image sensor ofclaim 6, wherein a distance between the bonding conductors is differentfrom a distance between the peripheral bonding conductors.
 8. A imagesensing device comprising: an infrared (IR) emitter emitting an IR lightto an object; and a three-dimensional (3D) image sensor receiving areflected light via a lens and analyzing color information and distanceinformation of the object, wherein the 3D image sensor includes a pixelarray, the pixel array including upper pixels disposed in a firstsubstrate and including at least one photogate and at least onephotoelectric element to sense the reflected light, lower pixelsdisposed in a second substrate and including at least 3 transistors todetect a pixel information from an output signal of the photogate to anelectric signal, and bonding conductor array disposed between the firstsubstrate and the second substrate and electrically connected with theupper pixel and corresponding lower pixel, wherein an upper pixel arrayis disposed in rows and columns of a first arrangement and the bondingconductor array is disposed in rows and columns of a second arrangement,wherein the second arrangement is inclined with respect to the firstarrangement.
 9. The image sensing device of claim 8, wherein the firstarrangement includes rows in a first direction and columns in a seconddirection in planar, the second arrangement includes rows in a thirddirection and columns in a fourth direction in the planar, and the firstdirection is inclined to the third direction and the second direction isinclined to the fourth direction.
 10. The image sensing device of claim8, wherein the number of the bonding conductors in a pixel unit is sameas the number of photogates in the upper pixel of the pixel unit. 11.The image sensing device of claim 8, wherein the upper pixel includes atleast one photoelectric element converting the reflected pulse signaland at least one photogate outputting an electric signal, and the lowerpixel includes a plurality of transistors to detect the colorinformation and the distance information from electric signal.
 12. Theimage sensing device of claim 11, wherein the bonding conductor isconnected across the photogate in the first substrate and a transfertransistor among the plurality of transistors in the second substrate.13. The image sensing device of claim 11, wherein the upper pixel arrayincludes at least four pixels disposed in rows and columns of the firstarrangement, the bonding conductor array includes at least four bondingconductors disposed in rows and columns of the second arrangement, and adiagonal length of the first arrangement is same as a horizontal lengthof the second arrangement.
 14. A three-dimensional (3D) image sensorcomprising: a pixel array including a pixel region and a peripheralregion; and peripheral circuits to detect color information and depthinformation, wherein the pixel array includes: upper pixels disposed ina first arrangement in a first substrate, lower pixels disposed in asecond substrate, and bonding conductor array disposed between the firstsubstrate and the second substrate and electrically connected with theupper pixel and corresponding lower pixel, wherein the bonding conductorarray includes in same planar: pixel bonding conductors disposed in asecond arrangement under the pixel region; and peripheral bondingconductors in a third arrangement disposed under the peripheral region,wherein the first arrangement is inclined with respect to the secondarrangement.
 15. The 3D image sensor of claim 14, wherein the firstarrangement includes the pixels disposed in rows in a first directionand columns in a second direction which is orthogonal of the firstdirection, the second arrangement includes the pixel bonding conductorsin rows in a third direction and columns in a fourth direction which isorthogonal of the third direction, wherein the first direction and thethird direction are inclined with respect to each other.
 16. The 3Dimage sensor of claim 15, wherein the third arrangement includes theperipheral conductors in rows in a fifth direction and columns in asixth direction which is orthogonal of the fifth direction, and whereinthe third direction and the fifth direction are inclined with respectwith each other.
 17. The 3D image sensor of claim 15, wherein athickness of the peripheral bonding conductor is greater than athickness of the pixel bonding conductor.
 18. The 3D image sensor ofclaim 17, wherein a distance between the pixel bonding conductors isdifferent from a distance between the peripheral bonding conductors. 19.The 3D image sensor of claim 15, wherein the pixel region is surroundedby the peripheral region, wherein an array of the pixel bondingconductors is surrounded by the peripheral bonding conductors.